Grinding machine



sept.l 27, 193s. H r. SMITH GRIND'ING MACHINE' Filed-.June 5,' 195s 2 ysheets-sheet 1 n l L l 5 j I v Srweutor Gttornegs 'Ptented Sept.}27, 1938 UNITED `s'm'r1-:s-

PATENT OFFICE GEINDING MACHINE Herbert F. Smith, Springlield, Ohio Application .lune 3, 1938, Serial No. 211,641

friction together with the introduction of a controllable friction-imparting device.

In all plain screw and nut devices, whether intended to elevate or lower a weight or to move a weight in any direction, approximately 60% to 75% of the power imparted to the screw is absorbed in overcoming the frlctional resistance -of the screw threads ofthe screw with those of the nut. This frlctional resistance is the one thing that is relied upon in all bolt and nut devices to maintain parts in a bolted-together relation.l Very often advantage is taken of this inherent frictional resistance as a vsort of seltlocking feature whereby an element such asa work table or a tool-head of a grinding machine may be retained at a given elevation without other locking devices. -The resistance is not constant, however, depending on the state of lubrication of the parts and other causes such as varying loads applied to the movable part, and in the instance of machine tools where it is often de- Y sirable to indicate the amoimt of elevation or lowering by graduations on-a part associated with the screw, such. as a hand wheel, the ,readings are not an accurate index of the movement of the movable part, mainly due to the torsion of the rotary and partly to variations in the weights imposed on the threaded devices.

This invention is pariclnarly adaptable to incorporation .in machine tool design, and one of the objects of the invention is to so reduce the frictional resistance before mentionedas to eliminate to a greatextent the angular variation in graduation readings due to torsion oi' the parts,

both in elevation and lowering, more especially referring to lowering in connection with the' de'- scent of a tool-head when nearV or in contact with the work. Y. Y

Another object of the invention is the provision of a controllable irictional resistance imparting device such as a brake to prevent coasting of the movable part. ASince so little friction remains by the use of the improved nut.'

the self-locking feature disappears, and coasting may follow. Inasmuch as nospecial reliance could be placed on frictional resistance as a self-- lock, due tovthelenature ofthe resistance as previously mentioned, there is preferably provided instead 'a controllable device to act as a self-lock, and as a further object and lever mechanical advantage, therefore. the brake can be small and of inexpensive design. The

amount ofresistance set up by the brake can 10 be controlled or varied easily to make up for variations in the weight of the movable parts such as may occur when tools of Yvarying weights are carried by the tool-head. Y

Another object and advantage is the obvious 16 reduction in power required to operate the machine. In the accompanying drawings:

Fig. '1 is a front elevation of a grinding machine in whichdevlces embodying the principles 20 otv the invention are incorporated, those portions of the machine which are old in the art being shown in broken lines, while the novel featlnes and -adjacent machine surfaces are shown in full lines. j A Y Fig. 2 is a fragmentary vertical section on the line 2-2 of Fig. 1, the same remarks as to broken and full line showings also applying to this view, the view being on a larger scale as compared to- F18. 1.

Fig.3 isavlewonastill largerscale, partly in elevation and partly in section, the section beingtakenonthelineI- ofFig. 2 anadjacent portion ofthe machine being herein shown in full lines.

Fig. 4 ris an enlarged fragmentary section on thelinel-l'ofFigslandZ.

Fig. 5 -is an enlarged front elevation of the brake mechanism, the view being partly broken f away to show interior parts in section. Pig. 6 is a. frontelevation of the brake mechanism with portions broken away and shown section. 4 Inthepresentcasetheinventionhasbeen vshown applied tofagrinding machine, although not limited to that particular machine, and only those parts of a grinding machine necessary to illustrate the installation of the invention thereon will be described. j Referring to the drawings, I represents a bese on which is slidably mounted for reciprocatory motion a.- work-table 2, the means for actuationk of which is not shown inthe present instance. A eohxmnlisattaehedtothebesebymea'nsnot. shown, and on the column is slidably mounted ss for vertical travel thereon a saddle 4. :As is customary with machines of the type shown, the

saddle 4 'supports a sliding wheel or tool head 5 arranged to slide transversely to the longitudinal travel of the work table 2, which is from left to right and vice versa in Fig. 1. The slide rotatably supports a spindle 6 which in turn carries an abrasive grinding wheel 1. .Y

To elevate or lower the grinding wheel 1 from or toward the work-table is; the function of the elevating mechanism now to be described. 'Ihe saddle 4 is supported by a threaded screw 8 depending from a radial anti-frictional bearing 8, the inner race-of which is attached to the screw and the outer race of which is supported in a re- 'cess 3' inthe upper portion ofthe column 8, as

shown inFig. 2. The engagement of the screw withthe saddle 4 is by means of the improved nut indicated in generalat II) attached to an adjacent portion 4 of the saddle 4. The' specific construction of the nut I8 will appear later.

The lower end 8' of the screw 8 is inserted slidably in an anti-friction bearing Il received in a. suitable recess in the base I, as shown in Fig. 2. On the lower end of the screw 8 is keyed a bevel gear I2 whose hub rests on the inner race of the bearing I I, and meshingwiththe gear I2 is a bevel pinion I3 secured to the,inner end of a cross-shaft I4 suitably supported for rotation on anti-friction bearings I5 carried in the base I and anti-friction bearings I8 shown in dotted lines and located in a housing herein'- after-referred to carried by the base. The outer end of the cross-shaft I5 projects through the forward wall I' of the base I, and on' the outer end there is preferably secured a hand wheel I1. Preferablyl the ratio of the bevel-gearing just mentioned is of the nature of two to one, whereby the labor of the operator in raising the saddle is reduced.

It can be seen that in reducing the thickness of a piece of work held by any means on the work-table 2 by peripheral contact ofthe grind# ing wheel with the work, the grinding wheel 1 is successively let ldown toward the work, and the lowering of vthe wheel in certain very small amounts is of rather greater importance than the mere greater ease of operation in elevating the wheel.

vTo aid the operator in knowing within cer` tain limits of tolerance Just how far to lower the grinding wheel, there is Preferably PIOVlded a series of equally divided graduations (not shown) on the periphery of the hand whe'el I1. In reality, to get a good legible distance between graduations, the radius of .the hand wheel I1 is often increased which increment is often e'ective in y more readily setting up torsion in the cross shaft -grinding wheel is actually being lowered an amount as represented by the graduations.

` Referring now to Fig. 3, the nut is seen to consist of a main body portion I8 attached by screws I9 to the adjacent saddle portion 4' of the saddle 4. Standing at right angles to the body portion I8 is a pair of integrally attached ears, there being an-upper, heavier ear 2l and a lower ear 2l, having aligned openings 28' and 2l', through which the screw 8 is inserted. The

means for reducing the former objectionable thread friction consists of a plurality of coaxially aligned rolls rotatably supported by anti-friction radial bearings carried in the ears 28 and 2| To this end, a plurality of equally spaced, aligned `openings 22, in parallel co'ax ial relation with the axis of rotation of the screw, are provided in the ears 20 and 2l, and since in the present case three rolls are employed, there are three openings 22 in the upper ear 20 and three openings 22 in the lower ear 2|. v

'I'he rolls 23a, 2lb' and 28oA themselves are identical in the present instance, therefore in the description, one roll 28a only is treated, it being understood the same reference characters apply to any one of the three rolls. The outer cylindrical surface of each roll is grooved with.

peripheral straight parallel grooves 24, each groove being spaced apart from its neighboring groove a distance equal to the pitch of the threads of the screw 8 and a land 25 ofthe roll is a counterpart of the space between adjacent threads of the screw, and a groove 24 is a counterpart of the thread of the screw.

At each end of the roll 23a there is provided a reduced-diameter extended trunnion 26, and on each trunnion an anti-friction bearing 21 is fitted. These bearings 21 are inserted in the previously mentioned openings 22 which are boredtosuch size as to snugly receivethe bearings.l 1

I`n^the assembly of the nut, each roll is in- .serted loosely in its place, in the present instance with'outhaving the bearings either in ,place on the rolls ,or in their respective bore, `and preferably before the screw 8 is assembled into the machine. Each roll may be inserted l'oosely in place from the outside by inserting an end, say the upper end, into 'a bore cavity then lifting the roll to a suillcient height to allow the lower trunnion to pass over the inner face of the lower ear 2| so asito place the lower trunnion into its bearing ibore. The bearings are then slipped into place in the bearing bores, while at the same time an adjacent trunnion is being received into the bore of the inner race, the bearing coming to'a stop against a shoulder on the trunnion. A washer shown at 28 preferably having a shallow central recess in one side is then inserted in each bearing bore 22 against the bearing 21. The purpose of this washer will appear later.v

The screw 8 is-then threaded into the vnut assembled thus far. A'ilnal adjustment is necessary involving lendwise shifting of each roll because as Vmight be inferred, each roll being identical, there will be a difference in the positioning' of each roll with 'respect to each other due to the pitch of the thread on the screw. That is, taking the roll 28a. (Fig. 3) as a basic roll and witlr' a right hand screw as shown, the roll 28h will be shifted axially until it is one-third the pitch higher than the roll 28a. and in a similar manner the roll 28e will be one-third the pitch higher than the roll 2lb or a total of two-thirds the pitch higher for nerradjustment with a view to insuring that I each roll will take its respective share of the load,

the means also providing that such adjustments y are permanently maintained.

For this purpose .there is provided in the present instance a pair of overlying plates, one of which,

indicated at 28 overlie's the upper surface ofthe 75 u 'Y upper ear 2B and-'is paratively long bolts 33 are passed through openis practically eliminated.

partially secured to the nut body by the screw 30, while another plate 3| is ysecured in a similar manner adjacent the lower surface of thelower ear 2|, a screw 32 being employed in the same manner as the screw 30. To provide greater rigidityand strength, comings in ears and plates and through the bores of tubular spacing -members 34 which. being the same length as the space between the inner faces of the ea'rs, serve to prevent distortion when the n uts 35 are tightened.

'Ille plates 29 and 3| overlie and close the outer ends of the bearing bores 22, and in those portions of the plates in alignment with the longitudinal axes of the rolls there are provided threaded vopenl ings into which adjusting screws 3B are threaded.

On adjustment, each of the screws 36 make contact with an adjacent washer 28, which with its centrally-located recessed side placed toward a bearing 21 provides that the pressure of the screws 36 is imposed on the outer race of the corresponding bearing 2l.

Therefore, it will be seen that by letting out a screw 3S positioned at one end of a roll 23 and turning in the similar screw 38 at end of the roll, the roll itself may be shifted axially, the bearings ofthe roll in question sliding in their bores to a like extent. With suitable gauges, each yroll may vbe adjusted so as to be assuredV beforehand that each roll will in time take its proper share of the load imposed on the When the screw 8 is rotated as by hand manipulation of thehand wheel l1, it'will be seen that the'rolls l23a,'23l and 23o turn 'about their own axes due tothe contact of the rolls with the screw, but with only a small amount of friction since the rolls are carried by the antifriction bearings 21. In this way the thread friction incidental to plain nut an screw'arrangements t will be understood that the rotation of .the screw and rolls in either direction either elevates or lowers the saddle 4 and load carried thereby, which in the present case is the saddle, tool head-and tool carried thereby.

With a machine of the type illustrated in the drawings, or in any machine in which a comparatively heavy part is elevated along a substantially vertical column such as the present column 3, the force of gravity tends to cause the part to descend, the undesirable descent being heretofore held. in check by the thread friction, assistance in varying degree in preventing undesirable descent or coasting being provided by the inertia. of the revoluble parts of the elevating mechanism.

vin all instances, therefore, thev inertia of the revoluble parts variesgbeing large with a high ratio and vice versa. Undesirable descent or coasting could initiate itself from jars or vibra'- tions from any source, to Aprevent which there is preferably employed a small controllable frictionimparting device or brake, making the-same adjustable so that the degree of friction imposed can b e varied accordingly as the inertia of the revoluble parts varies. Further, although the Y brake device may be located at any one of several points with reference tothe revoluble elevation parts and the necessary amount of friction im' the opposite posed at that point it is preferable to locate the brake device so as to apply-the added friction' to the hand wheel (preferably to the rear side thereof). 'I'his location is suitable for the reason that a change in the degree of friction may be quickly made, this being a desirable feature' in view of a change in the weightof the part to be elevated. as when other tools are added to a tool head. Also, in view of the desirability of -providing that graduations indicate very nearly the -linear movements of the part being moved, the

location at the` hand wheel is preferable since in the present instance no part ofthe cross-shaft or screw is putin torsion in overcoming the small frictional resistance.

'Ihe frictional device employs a small ilat plate 38 (Figs. 5 and 6) having a facing 39 preferably` of a fibrous frictional materialsuch as brakehollow exteriorly peripheral surface of the housing. 44 attached to the forward surface of the base I concentrically disposed with relation to the cross shaft i4 and carrying the forward bearing I6 heretofore "referred toland supporting this end of the cross shaft I4. Between the forward end of the screw 42 and the rearward side of the plate 38 is inter'- posed a coiled spring th-which exerts pressure in greater or less degree on the frictional facing 39 on. the rearward side of the hand wheel l'l,l the friction being varied by adjustably out the screw 42. A look nut 41 .is employed to retain the screw 42 in any adjusted position. s

Having thus described my invention, I claim: 1. In aV screw operated raising and lowering mechanism, a weight supporting element, a screw. devices for rotating said screw, a series o f grooved rolls supporting said element meshed with the mechanism, a weight supporting element, a screw.' devices for rotating said screw, a series of grooved rolls supporting said element meshed with the threads of said screw together with anti-friction bearings between said element and rolls, a fricv tion brake for the revoluble parts, said friction brake comprising ashoe bearing upon a portion of the revoluble parts, a spring for pressing said shoe into frictional engagement with said parts.

andmeans for adjusting the tension of said s spring:

4. In a grinding machine, a saddle, a grinding wheel supported by said saddle, a screw. 'devices for rotating said screw, a series of grooved rolls supporting said saddle meshed with the threads of saidscrew together with anti-friction bearings between said saddle androlls, a friction brake for therevoluble parts, said friction brake comprising a shoe bearing upon a portion of the revoluble parts, a spring .for pressing said shoe screwing in or a grinding `threads of said screw together with anti-friction and rolls, and a friction Y into frictional engagement with said parts, and means for adjusting they tension of said spring.

5. In a screw operated raising and lowering mechanism, a weight supporting element having a pair of spaced ears, a screw passing loosely through said ears, devices for rotating said screw, a series of grooved rolls interposed between said ears meshed with the threads of said screw to,

tween said ears meshed with the threads of said screw together with anti-friction bearings between said saddle and rolls, and a friction brake for the revoluble parts.

7. In a screw operated raising and lowering mechanism, a weight supporting element having a pair of spaced ears, a screw passing loosely through said ears, devices for rotating said screw,

oluble parts, said friction brake comprising a shoe bearing upon a portion of the revoluble parts, a spring for pressing said shoe into frictional engagement with said parts. and means for adjusting the tension of said spring.

8. In a grinding machine, a saddle having a pair of spaced-apart ears, a grinding wheel supported by said saddle, a screw passing loosely through said ears, devices for rotating said screw, a series of grooved rolls interposed between said ears meshed with the threads of said screw together with anti-friction bearings between said saddle and rolls, and a friction brake for the revL oluble parts, said friction brake comprising a shoe bearing upon a portion of the revoluble parts, a spring for pressing said shoe into frictional engagement with said parts, and means for adjusting the tension of said spring.

HERBERT F. SMITH. 

